(1) Field of the Invention
This invention relates to Q-switched lasers and, more particularly, to a method and apparatus for controlled slow Q-switching.
(2) Description of the Prior Art
Q-switching is a commonly-used method for achieving high pulse power from a laser. The method involves first pumping a laser medium while the optical "Q" of the laser resonant cavity is kept low, during which laser emission is prevented and energy is stored in the laser medium; then "switching" the Q to a high value, at which the stored energy is released in the form of a very short ("giant") pulse.
Generally, it is considered desirable to minimize the time for switching the Q of the resonant cavity in order to insure the efficient production of a single large pulse. However "slow" Q-switching has also been studied (see, e.g., Solid-State Laser Engineering, W. Koechner, Springer-Verlag, New York (1976), pp. 402-404). Slowly Q-switched lasers were disclosed by Midwinter, who simulated Q-switching using a rotating mirror (Brit. J. Appl. Phys. 16, 1125 (1965)), and by Newbery, who reported on experiments involving an electro-optically Q-switched CaWO.sub.4 :Nd laser (Brit. J. Appl. Phys. (J. Phys. D.), 1, 1849 (1968)). In both cases, it was reported that multiple pulses result for long switching times.